Precision detent system



April 1967 A. w. RYBERG 3,314,301

PRECISION DETENT SYSTEM Filed Sept. 4, 1964 V 2 Sheets-Sheet l 11,111,,I I 1 IlrIIll 1/ IIIIIIIIII F/GJ INVENTOR flRu/va 14 RY8ERG BY?4 W ,6ATTORNEY April 1967 A. w. RYBERG 3,314,301

PRECISION DETENT SYSTEM Filed Sept, 4, 1964 2 Sheets-Sheet 2 615' FIG. F16.7

XNVENTOR film/N6 14 Breezes.

W0. AM

4.; ATTORNEY United States Patent This invention relates generally todetent systems for rotary members, and more particularly to noveldetents that provide precise settings with a high degree of positionrepeatability.

Variable attenuators for microwave signals of the order of tenkilomegacycles and above, in general practice, are of the lossy-cardtype mounted within a rotary cylinder. The angular setting of theattenuator cylinder, with respect to fixed coupling wave guides,determines the attenuation effected. Where discrete accurate steps ofattenuation are desired, precise and direct angular settings arerequired. Further, in a practical attenuator, maintenance of itsresettability is important. The detentsystem of this invention isdirected to provide a simple, inexpensive and effective solution to suchdifl'lcult requirements. The elements and features of the novel detentarrangement hereof are applicable to other rotary devices, as well.

Another advantage of the detent mechanism herein set forth is thatdiscrete angular positions of the attenuator that are very closetogether can be readily accommodated. Each detent arm or followeroperates independently. They are displaced laterally and coact withprecisely positioned grooves on the circular surface of the drum orcylinder. The novel detent followers hereof are arranged with lowinternal tensions, to maintain their precision action. Their adjustmentin gross and even vernier adjustment is easily accomplished and remainpreset. A cantilevered clamp bar is interlinked with each detentfollower into a stable array.

The above and other features, advantages and objects of this inventionwill become more apparent in the following description of an exemplaryembodiment thereof, illustrated in the drawings, in which:

FIG. 1 is the front view, partially broken away, of the exemplarymicrowave attenuator incorporating the invention detents.

FIG. 2 is the rear view of the attenuator of FIG. 1, partially brokenaway, showing the detents thereof.

FIG. 3 is the top view of the device of FIGS. land 2', partially insection.

FIG. 4 is the cross-sectional view taken along the line 44 of FIG. 3, inthe direction of the arrows.

FIGS. 5 and 6 are respectively elevational and side views of a detentfollower hereof.

FIG. 7 is an enlarged side view of the detent tip.

FIGS. 8 and 9 are respectively plan and side views of the cantileverclamp bar.

FIG. 10 is a perspective illustration of a detent assembly.

The microwave attenuator is a step device with preset precise detentedpositions selectively attained through knob 16 and shaft 17. The device15 is enclosed in a frame 18. The control shaft 17 is geared tooperating shaft 20 by bevel gears 21, 22 (see FIGS. 3 and 4). The rotarycylinder contains a shaped lossy-card or vane 24 cemented therewithin,in a plane through its axis. Cylinder 25 contains a series oflongitudinal surface grooves 26, at one end, that engage with drive gear27. Gear 27 is rotated by shaft 20, whereby the cylinder 25 is angularlydisplaced through knob 16.

The angular position or setting of the vane 24 determines the resultantattenuation. The central cylinder 25 is joined at each end with fixedtransition wave guides 28, 29- The microwave signals to be attenuatedare fed 3,314,301 Patented Apr. 18, 1967 into guide 28, pass throughrotary section 25, and out through guide 29; or vice versa. Eachtransition wave guide contains a central fixed vane (not shown) tocomplete the. attenuation array. The bearings of cylinder 25 aresuitably set in its juncture with guide 28, 29, and arranged to alsoserve as radio frequency chokes.

The predetermined angular settings of rotary cylinder 25 are determinedby corresponding longitudinal grooves 30, 30 precisely formed on thecylinder surface. Coacting with respective grooves 30, 30 are associateddetent followers 31, 31that are positioned very accurately, in theinvention system. The relatively wide tip 32 of each detent 31 engagesits groove 30 in a firm manner, over a substantial extent. This servesto stably hold the attenuator setting. The detent 31' at the left end ofFIG. 2 is shown meshed in groove 30'. The detents 31, 31 arelongitudinally displaced along the cylinder 25 in individual positions.In this manner, each presetting of the grooves 30, 30 is independentlylocatable, even in very close angular relation to each other. Theexemplary detent followers 31, 31 are of spring steel .025 inch thick,0.5 inch wide, and about one inch long.

Each detent follower 31, 31 is adjustably supported substantiallytangent to the surface of cylinder 25. In the illustrated embodiment thedetents 31, 31 are vertically mounted and exposed at the rear of theunit 15, as seen in FIGS. 2, 4 and 10. A horizontally disposed clamp bar35 contains a lug 33 inserable in an aperture 37 of the detent 31, forholding it by cantilever action. Each clamp bar 35 has a bent centralportion for presenting a projecting lug 33 above the support base 34.The tip of machine screw 36 is threaded into opening 37 of bar 35 forsecuring or loosening its associated detent 31. The cantilever clamp bar35 is fastened to base 34 by screw 38 at threaded aperture 39 (see FIG.4.) The clamp bars are made of spring steel to effect spring action insupporting the detents 31, 31. The exemplary clamp bar is .0625 inchthick, .5 inch wide and about 1.25 inch overall.

I The bottom region of each-detent follower 31 has a rectangular cut-out40 that rests upon a set-screw 41. The set-screws 41, 41 are threadedinto base 34. In this manner the height of the tip 32 of each detentfollower 31 abovethe base 34 is closely adjustable and set, as indicatedby the arrows a. The thus preset detents 31, 31 are secured in theirrespective settings by the pressing down of their corresponding clampbars 35, 35 through screws 36, 36 as indicated by the arrows b. It isnoted that the lugs 33, 33 extending from bars 35, 35 are bentdownwardly in apertures 37, 37 of detents 31, 31. This results in aspring bias, holding the detent tips 32, 32 pressed against the surfaceof the cylinder 25. Bars 35 are held set by the screws 36 in openings37a.

The detent tips 32, 32 are shaped for accurate seating in theirrespective surface grooves 30, 30 and still ride over the surface of thecylinder with a minimum of friction. In this way the cylinder 25 isreadily rotatable through the knob 16 and associated gearing to thecalibrated discrete attenuator settings, wherein the correspondingdetent follower 31 engages the groove 30 involved to precisely positionthe contained vane 24 and firmly maintain its setting. The settingaccuracy is accomplished through the minimizing of detent springtensions in their operation and state.

The adjustment of each detent follower 31, 31 is readily accomplished asfollows: The cantilever clamp bar 35 is loosened through its screw 36.The set-screw 41 is then turned to correspondingly raise or lower thedetent tip 32 until it seats snugly in its groove 30 on the cylinder 25.The attenuator vane 24 is close to its calibrated angular position whilethe gross adjustments thus far described, are being made. The clamp bar35 is thereupon tightened through the screw 36 sufficiently for thedetent tip 32 to press firmly in its groove 30. The vernier location ofthe detent is then accomplished by set-screw 41 adjustment, by slightlyangularly displacing the cylinder 25 through the tip 32.

Precise vane 24 positions are indicated by external calibrationequipment. The invention detent system effects setting or positionrepeatability over long periods of operation within an accuracy ofL0.0005" along the cylinder 25 circumference. An attenuator cylinder 25of one inch diameter thus affords discrete attenuation steps withexcellent repeatability and calibration maintenance in practical fielduse. The angular location of the index grooves 30, 30 on the cylindersurface corresponds to the desired attenuation steps; the precisionsetting of the associated detent followers 31, .31 provides therequisite accuracy of the attenuation results.

While the present invention has been illustrated and described inconnection with a particular embodiment thereof, it is to be understoodthat it may be practiced in other forms and arrangements within thebroader spirit and scope of the invention as set forth in the followingclaims.

I claim:

1. A detent system for a rotary member comprising at least one detentsection composed of a detent follower coactable with a correspondinggroove on the peripheral surface of the member and a clamp bar formaintaining said follower pressed against the member and for engaging itwith its associated groove in detenting action for the rotary member,said clamp bar having a projection coupled with said follower anddisposed to bias it towards the member, and a set-screw for the Vernieradjustment of said follower.

2. A detent system for a rotary member of cylindrical form comprising atleast one detent section composed of a detent follower with a lipcoactable with a corresponding groove arrayed longitudinally on theperipheral surface of the member and a clamp bar for maintaining the lipof said follower pressed against the cylindrical surface and forengaging it with its associated groove in precise detenting action forthe cylindrical member, said clamp bar having a projection coupled withsaid follower in cantilever array and disposed to bias it towards themember surface, said detent follower being substantially tangent to themember surface, and a set-screw in line with the follower for itsVernier adjustment.

3. A detent system for a rotary member of cylindrical form comprising aplurality of detent sections each composed of a detent follower with alip coactable with a corresponding groove arrayed longitudinally on theperipheral surface of the member and a clamp bar for maintaining the lipof said follower pressed against the cylindrical surface and forengaging it with its associated groove in detenting action for thecylindrical member, each said clamp bar having a projection coupled withits follower and disposed to bias it towards the member surface, and aset-screw for the Vernier adjustment of each of said followers.

4. A detent system as claimed in claim 3, in which said detent followersare arranged seriatim along the cylindrical surface in a substantiallycommon plane.

5. A detent system for a rotary member of cylindrical form comprising aplurality of detent sections each composed of a detent follower ofresilient material with a lip of substantial width coactable with acorresponding groove arrayed longitudinally on the peripheral surface ofthe member and a clamp bar for maintaining the lip of said followerbiased towards and pressed against the cylindrical surface and forengaging it with its associated groove in precise detenting action forthe cylindrical member.

6. A detent system as claimed in claim 5, in which each said clamp barhas a projection coupled with its follower in cantilever array anddisposed to hold it against the member surface, said detent followersbeing substantially tangent to the member surface, and a set-screw inline with each follower for its Vernier adjustment of each of saidfollowers.

7. A detent system as claimed in claim 5, in which said detent followersare arranged seriatim along the cylindrical surface in a substantiallycommon plane with their corresponding grooves angularly positioned forthe desired detenting stops and axially disposed in respective alignmentwith the followers.

8. A detent system as claimed in claim 5, in which said detent followersare arranged seriatim along the cylindrical surface in a substantiallycommon plane with their corresponding grooves angularlypositioned forthe desired detenting stops and axially disposed in respective alignmentwith the followers.

References Cited by the Examiner UNITED STATES PATENTS FRED C. MATTERN,JR., Primary Examiner. J. l). BUFFER, Assistant Examiner.

1. A DETENT SYSTEM FOR A ROTARY MEMBER COMPRISING AT LEAST ONE DETENTSECTION COMPOSED OF A DETENT FOLLOWER COACTABLE WITH A CORRESPONDINGGROOVE ON THE PERIPHERAL SURFACE OF THE MEMBER AND A CLAMP BAR FORMAINTAINING SAID FOLLOWER PRESSED AGAINST THE MEMBER AND FOR ENGAGING ITWITH ITS ASSOCIATED GROOVE IN DETENTING ACTION FOR THE ROTARY MEMBER,SAID CLAMP BAR HAVING